Wire, heat exchanger, and magnetic heat pump device

ABSTRACT

[Solving Means] An outer surface 121 of a wire 12A formed of a magnetocaloric material having a magnetocaloric effect partially has at least one of a concave portion 122 and a convex portion 123, the concave portion 122 is recessed in a radial direction of the wire 12A, and the convex portion 123 protrudes in the radial direction in a longitudinal direction of the wire 12A.

TECHNICAL FIELD

The present invention relates to a wire used in a magnetic heat pumpdevice using a magnetocaloric effect, and a heat exchanger and amagnetic heat pump device including the wire.

The present application claims priority from Japanese Patent ApplicationNo. 2017-155813 filed on Aug. 10, 2017. The contents described and/orillustrated in the documents relevant to the Japanese Patent ApplicationNo. 2017-155813 will be incorporated herein by reference as a part ofthe description and/or drawings of the present application.

BACKGROUND ART

In order to suppress an increase in pressure loss, a heat exchanger isknown in which a plurality of linear magnetic bodies are inserted in atubular casing while being overlapped in a direction intersecting thelongitudinal direction of the magnetic body (for example, see PatentDocument 1).

CITATION LIST Patent Document

Patent Document 1: JP 2013-64588 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

When a magnetic heat pump device reaches a steady state, a temperaturegradient is generated in the heat exchanger so that a uniformtemperature span is formed between a high temperature end and a lowtemperature end of the heat exchanger. It is desirable that thetemperature span become wider and thus the applicability of the magneticheat pump increases. However, there is a problem in which theabove-described linear magnetic body has a narrow temperature spancompared to a granular magnetic body.

An object of the invention is to provide a wire capable of obtaining awide temperature span and a heat exchanger and a magnetic heat pumpdevice including the wire.

Means for Solving Problem

A wire according to the invention is a wire which is formed of amagnetocaloric material having a magnetocaloric effect, in which anouter surface of the wire partially has at least one of a concaveportion and a convex portion in a longitudinal direction of the wire,the concave potion is recessed in a radial direction of the wire, andthe convex portion protrudes in the radial direction.

In the above-described invention, the wire may have a non-circularcross-sectional shape, and a cross-sectional shape at one position inthe longitudinal direction and a cross-sectional shape at the otherposition in the longitudinal direction may have a rotational symmetryrelationship.

In the above-described invention, the wire may have a non-circularcross-sectional shape, and the wire may be twisted in a circumferentialdirection of the wire.

In the above-described invention, the cross-sectional shape of the wiremay include an oval shape, a semi-circular shape, or an n-polygonalshape (n is a natural number from 3 to 8).

In the above-described invention, a cross-sectional shape at oneposition in the longitudinal direction and a cross-sectional shape atthe other position in the longitudinal direction may be different fromeach other.

In the above-described invention, a cross-sectional area at one positionin the longitudinal direction and a cross-sectional area at the otherposition in the longitudinal direction may be different from each other.

In the above-described invention, the wire may have a columnar shapehaving at least one of the concave portion and the convex portion.

In the above-described invention, at least one of the concave portionand the convex portion may include at least one of a wall and a grooveformed on an outer surface of the wire, and an extending direction of atleast one of the groove and the wall may include at least thecircumferential direction of the wire as an element.

A heat exchanger according to the invention is a heat exchangerincluding: an assembly which is obtained by bundling a plurality of theabove-described wires; and a casing which accommodates the assembly.

In the above-described invention, the casing may include a first openinglocated at one end portion and a second opening located at the other endportion, and a direction from the first opening to the second openingmay substantially match the extending direction of the assembly.

A magnetic heat pump device according to the invention is a magneticheat pump device comprising: at least one of the above-described heatexchangers; a magnetic field changer configured to apply a magneticfield to the magnetocaloric material and change the magnitude of themagnetic field; first and second external heat exchangers respectivelyconnected to the heat exchanger through a pipe; and a fluid supplierconfigured to supply a fluid from the heat exchanger to the first orsecond external heat exchanger in synchronization with the operation ofthe magnetic field changer.

Effect of the Invention

In the invention, the outer surface of the wire partially has at leastone of the concave portion and the convex portion in the longitudinaldirection of the wire. Accordingly, since a flow of a fluid flowing onthe surface of the wire becomes turbulent and a heat transfer ratebetween the wire and the fluid can be enhanced, it is possible to obtaina wide temperature span.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an overall configuration of a magneticheat pump device in a first embodiment of the invention and is a diagramillustrating a state where a piston is located at a first position;

FIG. 2 is a diagram illustrating an overall configuration of themagnetic heat pump device in the first embodiment of the invention andis a diagram illustrating a state where the piston is located at asecond position;

FIG. 3 is an exploded perspective view illustrating a configuration ofan MCM heat exchanger in the first embodiment of the invention;

FIG. 4 is a cross-sectional view taken along the extending direction ofthe MCM heat exchanger in the first embodiment of the invention and is across-sectional view taken alone a line IV-IV of FIG. 3;

FIG. 5 is a cross-sectional view taken along a line V-V of FIG. 4;

FIG. 6 is a perspective view illustrating a wire in the first embodimentof the invention;

FIG. 7(A) is an end view when the wire is cut along a line VIIA-VIIA ofFIG. 6 and FIG. 7(B) is an end view when the wire is cut along a lineVIIB-VIIB of FIG. 6;

FIG. 8 is an end view when the wire is cut along a line VIII-VIII ofFIG. 6;

FIGS. 9(A) to 9(L) are end views illustrating a modified example of thewire in the first embodiment of the invention;

FIG. 10 is a side view illustrating a wire in a second embodiment of theinvention;

FIG. 11(A) is a cross-sectional view when the wire is cut along a lineXIA-XIA of FIG. 10 and FIG. 11(B) is a cross-sectional view when thewire is cut alone a line XIB-XIB of FIG. 10;

FIG. 12 is a cross-sectional view when the wire is cut along a lineXII-XII of FIG. 10; and

FIGS. 13(A) to 13(E) are side views illustrating a modified example ofthe wire in the second embodiment of the invention.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, a first embodiment of the invention will be described withreference to the drawings.

First Embodiment

FIGS. 1 and 2 are diagrams illustrating an overall configuration of amagnetic heat pump device in the first embodiment of the invention,FIGS. 3 to 5 are diagrams illustrating an MCM heat exchanger in thefirst embodiment of the invention, and FIGS. 6 to 8 are diagramsillustrating a wire in the first embodiment of the invention. FIGS. 9(A)to 9(L) are cross-sectional views illustrating a modified example of thewire in the first embodiment of the invention.

A magnetic heat pump device 1 of this embodiment is a heat pump deviceusing a magnetocaloric effect and includes, as illustrated in FIGS. 1and 2, first and second MCM heat exchangers 10 and 20, a piston 30, apermanent magnet 40, a low temperature side heat exchanger 50, a hightemperature side heat exchanger 60, a rotary pump 70, pipes 81 to 84,and a switching valve 90.

The first and second MCM heat exchangers 10 and 20 of this embodimentcorrespond to an example of the heat exchanger of the invention, thepiston 30 and the permanent magnet 40 of this embodiment correspond toan example of a magnetic changer of the invention, the low temperatureside heat exchanger 50 and the high temperature side heat exchanger 60correspond to an example of first and second external heat exchangers ofthe invention, the pipes 81 to 84 of this embodiment correspond to anexample of a pipe of the invention, and the pump 70 and the switchingvalve 90 of this embodiment correspond to an example of a fluid supplierof the invention.

The first MCM heat exchanger 10 includes, as illustrated in FIGS. 3 to5, an assembly 11 which includes a plurality of wires 12A, a tubularcasing (container) 13 which accommodates the assembly 11, and terminalmembers 17 and 18 which are connected to both ends of the casing 13.Since the first MCM heat exchanger 10 and the second MCM heat exchanger20 have the same structure, only the configuration of the first MCM heatexchanger 10 will be described below and the description of theconfiguration of the second MCM heat exchanger 20 will be omitted.

The wire 12A of this embodiment corresponds to an example of the wire ofthe invention, the assembly 11 of this embodiment corresponds to anexample of the assembly of the invention, and the casing 13 of thisembodiment corresponds to an example of the casing of the invention.

The wire 12A is composed of a magnetocaloric material (MCM) having amagnetocaloric effect. When a magnetic field is applied to the wire 12Aformed of the MCM, magnetic entropy decreases as electron spins arealigned and the wire 12A generates heat so that a temperature rises. Onthe other hand, when the magnetic field is removed from the wire 12A,the magnetic entropy increases as the electron spins become clutteredand the wire 12A absorbs heat so that a temperature falls.

The MCM forming the wire 12A is not particularly limited as long as itis a magnetic body. However, a magnetic body having a Curie temperature(Curie point) in a normal temperature range of about 10° C. to 30° C.and exerts a high magnetocaloric effect in a normal temperature range isdesirable. Detailed examples of such MCMs include gadolinium (Gd),gadolinium alloy, lanthanum-iron-silicon (La—Fe—Si) based compounds, andthe like.

As illustrated in FIGS. 6 to 7(B), the wire 12A has a squarecross-sectional shape when the wire 12A is cut along a directionsubstantially orthogonal to the longitudinal direction of the wire 12A.Further, the wire 12A is twisted in the circumferential direction of thewire 12A when rotating in the opposite directions at both ends of thewire 12A using the center of the wire 12A as a rotation axis. The“square cross-sectional shape” in this embodiment also includes thosehaving slight deformation by twisting (for example, those having sideedges curved slightly inward by twisting). Further, a method of formingthe wire 12A is not limited to the method of twisting a linear wire. Forexample, a straight wire may be pressed or rolled into a twisted shapeusing a metal mold or the like or a wire may be extruded into a twistedshape.

In this way, in this embodiment, since the wire 12A is twisted, an outersurface 121 of the wire 12A partially includes a concave portion 122 anda convex portion 123 in the longitudinal direction of the wire 12A asillustrated in FIG. 8. That is, in this embodiment, the wire 12A has across-sectional shape in which the outer surface 121 is partiallyprovided with the concave portion 122 and the convex portion 123 whenthe wire is cut along the longitudinal direction of the wire 12A. Theconvex portion 123 is formed by the ridge of the wire 12A and protrudesin the radial direction of the wire 12A. On the contrary, the concaveportion 122 is formed by surfaces between the ridges of the wire 12A andis recessed in the radial direction of the wire 12A. In this embodiment,since the concave portion 122 and the convex portion 123 are formed bytwisting the wire 12A, the concave portion 122 and the convex portion123 are periodically and alternately arranged in the longitudinaldirection of the wire 12A. FIG. 8 is a cross-sectional view when thewire 12A is cut along the longitudinal direction of the wire 12A.

Further, in this embodiment, since the wire 12A having a squarecross-sectional shape (that is, a non-circular cross-sectional shape) istwisted, the cross-sectional shape at one position (for example, a lineVIIA-VIIA illustrated in FIG. 6) in the longitudinal direction and thecross-sectional shape at the other position (for example, a lineVIIB-VIIB illustrated in FIG. 6) in the longitudinal direction have arotational symmetry relationship as illustrated in FIGS. 7(A) and 7(B).FIGS. 7(A) and 7(B) are end views when the wire 12A is cut along adirection substantially orthogonal to the longitudinal direction of thewire 12A.

Although there is no particular limitation, it is desirable that thewire 12A have a diameter in which a diameter of a circumscribed circlecircumscribing a rectangular cross-sectional shape of the wire 12A isabout 0.05 mm to 3 mm. Further, although there is no particularlimitation, it is desirable that a twist pitch P of the wire 12A beabout 10 to 50 times longer than the diameter of the circumscribedcircle of the wire 12A.

The cross-sectional shape of the wire is not particularly limited to theabove-described square shape as long as the shape is non-circular (thatis, a shape other than a perfect circle).

For example, as illustrated in FIG. 9(A), a wire 12Aa may have an ovalcross-sectional shape. In this case, since the wire 12Aa can be producedonly by pressing a wire having a circular cross-sectional shape and thentwisting the wire, it is possible to facilitate the production of thewire. The “oval cross-sectional shape” in this embodiment includes thosehaving slight deformation by twisting.

Alternatively, as illustrated in FIG. 9(B), the wire 12Ab may have asemi-circular cross-sectional shape. In this case, since the wire 12Abcan be produced only by forming a wire by a quenching roll method andthen twisting the wire, it is possible to facilitate the production ofthe wire 12Ab. The “semi-circular cross-sectional shape” in thisembodiment includes those having slight deformation by twisting.

Alternatively, as illustrated in FIGS. 9(C) to 9(F), the wire 12Ac to12Af may have an n-polygonal cross-sectional shape. Here, n is a naturalnumber of 3 to 8. The cross-sectional shape of the wire is not limitedto a regular n-polygon shape. For example, as illustrated in FIG. 9(G),the wire 12Ag may have a rectangular cross-sectional shape.Alternatively, as illustrated in FIG. 9(H), the wire 12Ah may have atrapezoidal cross-sectional shape. Although not specifically illustratedin the drawings, the wire may have a cross-sectional shape of aparallelogram or a rhombus. In this embodiment, the “n-polygonalcross-sectional shape” includes those having slight deformation bytwisting (for example, those having side edges curved slightly inward bytwisting).

Alternatively, as illustrated in FIG. 9(I), the wire 12Ai may have across-shaped cross-sectional shape or the wires 12Aj to 12Al may have astar-shaped cross-sectional shape as illustrated in FIGS. 9(J) to 9(L).Since the cross-sectional shapes of the wires 12Ai to 12Al illustratedin FIGS. 9(I) to 9(L) have portions recessed inward, it is possible tofurther improve a turbulence of a fluid generated on the surface of thewire. The “star-shaped cross-sectional shape” in this embodimentincludes those having slight deformation by twisting.

The assembly 11 is formed by bundling a plurality of the wires 12A. Theplurality of wires 12A are bundled (overlapped) in a directionintersecting the longitudinal direction of the wire 12A. In other words,the plurality of wires 12A are adjacent to each other so that the sidesurfaces of the wires 12A contact each other. At this time, since thewire 12A has a non-circular cross-sectional shape and is twisted asdescribed above, a passage 111 (see FIG. 5) is formed between the sidesurfaces of the wires 12A. The plurality of wires 12 constituting theassembly 11 may have substantially the same wire diameter or may havedifferent wire diameters. Further, in order to facilitate understanding,the assembly 11 is formed by the wires 12A which are fewer than theactual wires in FIGS. 3 to 5, but in fact, the assembly 11 includesseveral thousand to several tens of thousands of wires 12A.

The assembly 11 illustrated in FIGS. 3 to 5 is formed by simply bundlingthe plurality of wires 12A, but the configuration of the assembly is notparticularly limited thereto. Although not specifically illustrated, forexample, the assembly may be formed by twisting a plurality of wirestogether. Alternatively, an individual stranded wire may be formed bytwisting several wires and the assembly may be formed by bundling theplurality of stranded wires. That is, the “assembly formed by bundlingthe plurality of wires” in this embodiment also includes “strandedwires.”

As a method of twisting the wires, for example, collective twisting,concentric twisting, complex twisting, and the like can be exemplified.The collective twisting is a twisting method in which a plurality ofwires are bundled together and twisted in the same direction about theaxis of the assembly. The concentric twisting is a twisting method inwhich a plurality of wires are concentrically twisted around a corewire. The complex twisting is a twisting method in which child strandedwires each of which is obtained by twisting a plurality of wires byconcentric twisting or collective twisting are further twisted byconcentric twisting or collective twisting.

The casing 13 which accommodates the assembly 11 includes, asillustrated in FIGS. 3 to 5, an accommodation portion 14 and a lidportion 15 and has a tubular shape with a rectangular cross-section. Thecasing 13 is formed such that one end portion is provided with a firstopening 131 and the other end portion is provided with a second opening132.

The accommodation portion 14 includes a bottom portion 141 whichconstitutes a bottom plate of the casing 13 and a pair of side portions142 and 143 which constitutes both side walls of the casing 13. Anopening 144 is formed between upper ends of the pair of side portions142 and 143. As a result, the accommodation portion 14 has asquare-cornered U-shaped (substantially U-shaped) cross-sectional shapein a cross-section in a direction substantially orthogonal to the axialdirection thereof.

The lid portion 15 is a rectangular plate-shaped member. As illustratedin FIGS. 3 to 5, the lid portion 15 is fixed to upper ends of the pairof side portions 142 and 143. The opening 144 of the accommodationportion 14 is blocked by the lid portion 15 so that the casing 13 isformed.

The assembly 11 is accommodated in the casing 13 so that thelongitudinal direction (the extension direction (the longitudinaldirection) of the assembly 11) of the wire 12A constituting the assembly11 substantially matches the axial direction (a direction extending fromthe first opening 131 to the second opening 132) of the casing 13.Further, the centers of the first and second openings 131 and 132 arelocated to be substantially coaxial to the center of the assembly 11.Then, the passage 111 is formed between the wires 12A constituting theassembly 11 (see FIG. 5).

As illustrated in FIGS. 3 and 4, one end portion of the casing 13 isinserted into the first terminal member 17 and the first terminal member17 is fixed to the casing 13. Further, the other end portion of thecasing 13 is inserted into the second terminal member 18 and the secondterminal member 18 is fixed to the casing 13. As the first and secondterminal members (connection members) 17 and 18, for example, a heatshrinkable tube, a resin molded article, a metal processed article, orthe like can be used.

The first terminal member 17 includes a first connection port 171 whichis smaller than the first opening 131 of the casing 13. As illustratedin FIG. 1, the first connection port 171 communicates with the lowtemperature side heat exchanger 50 through the first low temperatureside pipe 81. The second terminal member 18 also includes a secondconnection port 181 which is smaller than the second opening 132. Thesecond connection port 181 communicates with the high temperature sideheat exchanger 60 through the first high temperature side pipe 83. Thecenters of the first and second connection ports 171 and 181 are locatedto be coaxial to the center of the assembly 11.

Similarly, an assembly 21 is also accommodated in the casing 23 of thesecond MCM heat exchanger 20 (see FIG. 2) and the assembly 21 is formedby bundling a plurality of wires 22A. Then, similarly to the first MCMheat exchanger 10, one end portion of the casing 23 is inserted into thefirst terminal member and the first terminal member is fixed to thecasing 23. Further, the other end portion of the casing 23 is insertedinto the second terminal member and the second terminal member is fixedto the casing 23. The second MCM heat exchanger 20 communicates with thelow temperature side heat exchanger 50 through the second lowtemperature side pipe 82 connected to a first connection port 271 of thefirst terminal member. Meanwhile, the second MCM heat exchanger 20communicates with the high temperature side heat exchanger 60 throughthe second high temperature side pipe 84 connected to a secondconnection port 281 of the second terminal member.

The wire 22A of the second MCM heat exchanger 20 has the sameconfiguration as the wire 12A of the first MCM heat exchanger 10.Further, the casing 23 of the second MCM heat exchanger 20 also have thesame configuration as the casing 13 of the first MCM heat exchanger 10,and the terminal members of the second MCM heat exchanger 20 also hasthe same configuration as the terminal members 17 and 18 of the firstMCM heat exchanger 10.

For example, in a case where an air conditioner using the magnetic heatpump device 1 of this embodiment is operated in a cooling mode, anindoor place is cooled by a heat exchange between the low temperatureside heat exchanger 50 and the inside air, and heat is emitted to anoutdoor place by a heat exchange between the high temperature side heatexchanger 60 and the outside air.

On the contrary, in a case where the air conditioner is operated in awarming mode, the indoor place is warmed by a heat exchange between thehigh temperature side heat exchanger 60 and the inside air, and heat isabsorbed from the outdoor place by a heat exchange between the lowtemperature side heat exchanger 50 and the outside air.

As described above, a circulation path including four heat exchangers10, 20, 50, and 60 is formed by two low temperature side pipes 81 and 82and two high temperature side pipes 83 and 84, and a liquid medium ispressure-fed in the circulation path by the rotary pump 70. As adetailed example of the liquid medium, for example, a liquid such aswater, an antifreeze solution, an ethanol solution, or a mixture thereofcan be exemplified. The liquid medium of this embodiment corresponds toan example of a fluid of the invention.

Two MCM heat exchangers 10 and 20 are accommodated inside the piston 30.The piston 30 can move in a reciprocating manner between a pair ofpermanent magnets 40 by the actuator 35. Specifically, the piston 30 canmove in a reciprocating manner between a “first position” illustrated inFIG. 1 and a “second position” illustrated in FIG. 2. As an example ofthe actuator 35, for example, an air cylinder or the like can beexemplified.

Here, the “first position” is a position of the piston 30 when the firstMCM heat exchanger 10 is not interposed between the permanent magnets 40and the second MCM heat exchanger 20 is interposed between the permanentmagnets 40. On the contrary, the “second position” is a position of thepiston 30 when the first MCM heat exchanger 10 is interposed between thepermanent magnets 40 and the second MCM heat exchanger 20 is notinterposed between the permanent magnets 40.

Instead of the first and second MCM heat exchangers 10 and 20, thepermanent magnet 40 may be moved in a reciprocating manner by theactuator 35. Alternatively, an electromagnet having a coil may be usedinstead of the permanent magnet 40. In this case, a mechanism of movingthe MCM heat exchangers 10 and 20 or the magnet is not necessary.Further, when the electromagnet having the coil is used, the magnitudeof the magnetic field applied to the wires 12A and 22A may be changedinstead of applying/removing of the magnetic field with respect to thewires 12A and 22A of the MCM heat exchangers 10 and 20.

The switching valve 90 is provided at the first high temperature sidepipe 83 and the second high temperature side pipe 84. In synchronizationwith the operation of the piston 30, the switching valve 90 can switchthe liquid medium supply destination of the rotary pump 70 to the firstMCM heat exchanger 10 or the second MCM heat exchanger 20 and switch theconnection destination of the high temperature side heat exchanger 60 tothe second MCM heat exchanger 20 or the first MCM heat exchanger 10.

Next, an operation of the magnetic heat pump device 1 of this embodimentwill be described with reference to FIGS. 1 and 2.

First, when the piston 30 is moved to the “first position” illustratedin FIG. 1, the wire 12A of the first MCM heat exchanger 10 isdemagnetized so that a temperature falls and the wire 22 of the secondMCM heat exchanger 20 is magnetized so that a temperature rises.

At the same time, a first path (the rotary pump 70 the first hightemperature side pipe 83 the first MCM heat exchanger 10 the first lowtemperature side pipe 81 the low temperature side heat exchanger 50 thesecond low temperature side pipe 82 the second MCM heat exchanger 20 thesecond high temperature side pipe 84 the high temperature side heatexchanger the rotary pump 70) is formed by the switching valve 90.

For this reason, the liquid medium is cooled by the wire 12A of thefirst MCM heat exchanger 10 of which a temperature decreases due to ademagnetization and the liquid medium is supplied to the low temperatureside heat exchanger 50 so that the low temperature side heat exchanger50 is cooled. At this time, since the liquid medium passes through thepassage 111 formed between the wires 12A inside the first MCM heatexchanger 10 so as to contact the wires 12A, the liquid medium is cooledby the wires 12A.

Meanwhile, the liquid medium is heated by the wire 22A of the second MCMheat exchanger 20 of which a temperature increases due to amagnetization and the liquid medium is supplied to the high temperatureside heat exchanger 60 so that the high temperature side heat exchanger60 is heated. At this time, since the liquid medium passes through thepassage formed between the wires 22A inside the second MCM heatexchanger 20 so as to contact the wires 22A, the liquid medium is heatedby the wires 22A.

Next, when the piston 30 is moved to the “second position” illustratedin FIG. 2, the wire 12A of the first MCM heat exchanger 10 is magnetizedso that a temperature rises and the wire 22A of the second MCM heatexchanger 20 is demagnetized so that a temperature falls.

At the same time, a second path (the rotary pump 70 the second hightemperature side pipe 84 the second MCM heat exchanger 20 the second lowtemperature side pipe 82 the low temperature side heat exchanger thefirst low temperature side pipe 81 the first MCM heat exchanger 10 thefirst high temperature side pipe 83 the high temperature side heatexchanger the rotary pump 70) is formed by the switching valve 90.

For this reason, the liquid medium is cooled by the wire 22A of thesecond MCM heat exchanger 20 of which a temperature decreases due to ademagnetization and the liquid medium is supplied to the low temperatureside heat exchanger 50 so that the low temperature side heat exchanger50 is cooled. At this time, since the liquid medium passes through thepassage formed between the wires 22A inside the second MCM heatexchanger 20 so as to contact the wires 22A, the liquid medium is cooledby the wire 22A.

Meanwhile, the liquid medium is heated by the wire 12A of the first MCMheat exchanger 10 of which a temperature increases due to amagnetization and the liquid medium is supplied to the high temperatureside heat exchanger 60 so that the high temperature side heat exchanger60 is heated. At this time, since the liquid medium passes through thefirst passage 111 formed between the wires 12A inside the first MCM heatexchanger 10 so as to contact the wires 12A, the liquid medium is heatedby the wires 12A.

When the above-described cycle is repeated, the cold and hot temperaturegenerated by the magnetocaloric effect is accumulated in the assemblies11 and 21, the side connected to the high temperature side pipe has ahigh temperature, and the side connected to the low temperature sidepipe has a low temperature. Then, when a temperature gradient is formedinside the first and second MCM heat exchangers 10 and 20 and the firstand second MCM heat exchangers 10 and 20 reaches a steady state, auniform temperature span ΔT is generated between the high temperatureend and the low temperature end. The temperature span ΔT is expressed bythe following equation (1). In the following equation (1), T_(h)indicates the temperature at the high temperature end in the steadystate and T₁ indicates the temperature at the low temperature end in thesteady state.

[Math. 1]

ΔT=T _(h) −T ₁  (1)

Here, Δq which indicates the heat quantity per unit time from the unitsurface area of the magnetocaloric material to the liquid medium isexpressed by the following equation (2). In the following equation (2),h indicates the heat exchange rate, T_(s) indicates the surfacetemperature of the magnetocaloric material, and T_(f) indicates thetemperature of the liquid medium.

[Math. 2]

Δq=h(T _(s) −T _(f))  (2)

Then, a state where the temperature span ΔT becomes uniform due to therepeated cycle (a state where the temperature span ΔT is saturated) is astate where the heat quantity Δq of the above-described equation (2) issufficiently small and a change ΔT_(f) of the refrigerant temperatureT_(f) for each cycle disappears. Thus, according to the above-describedequation (1), the magnitude of the temperature span ΔT depends on themagnitude of the heat transfer rate h.

In general, the heat exchange rate h in the above-described equation (2)is determined by the shape of the magnetocaloric material and thefilling method. Regarding some shapes such as a granular or linearshape, the heat exchange rate h is formulated by the Nusselt number Nu.That is, when the Nusselt number Nu is large, it can be considered thatthe heat transfer rate h is also large. Then, when the liquid mediumflows at the same speed, the Nusselt number Nu₁ of the granular materialcan be expressed by the following equation (3) and the Nusselt numberNu₂ of the wire can be expressed by the following equation (4). In thefollowing equations (3) and (4), Re is Reynolds number and Pr is Prandtlnumber.

[Math. 3]

Nu₁=2+0.6Re^(0.5)Pr^(0.33)  (3)

[Math. 4]

Nu₂=0.023Re^(0.8)Pr^(0.33)  (4)

According to the above-described equations (3) and (4), since theNusselt number Nu₂ of the wire is smaller than the Nusselt number Nu₁ ofthe granular material, it is understood that the heat transfer rate ofthe granular is lower than that of the wire. That is, the temperaturespan AT of the wire not twisted is narrower than that of the granularmaterial. The Nusselt number Nu₂ illustrated in the above-describedequation (4) is calculated on a condition that the flow of the liquidrefrigerant flowing on the surface of the wire is a laminar flow and theheat exchange between the wire surface and the liquid refrigerant isperformed by natural convection.

On the contrary, in this embodiment, the concave portion 122 and theconvex portion 123 are partially provided in the outer surface 121 ofthe wire 12A in the longitudinal direction of the wire 12A. Accordingly,the liquid medium flowing on the surface of the wire 12A collides withthe concave portion 122 or the convex portion 123 so that forcedconvection occurs and the flow of the liquid medium becomes turbulent.For this reason, since the heat transfer rate between the wire 12A andthe liquid medium can be improved, a wide temperature span can beobtained.

Second Embodiment

FIGS. 10 to 12 are views illustrating a wire in a second embodiment ofthe invention and FIGS. 13(a) to 13(e) are side views illustrating amodified example of the wire in the second embodiment of the invention.In this embodiment, the configuration of the wire is different from thatof the first embodiment, but the other configurations are the same asthose of the first embodiment. Hereinafter, only a difference betweenthe second embodiment and the first embodiment will be described.Further, the same reference numerals will be given to the samecomponents as those of the first embodiment and a description thereofwill be omitted.

A wire 12B of this embodiment has, as illustrated in FIGS. 10 to 11(B),a circular cross-sectional shape when the wire 12B is cut along adirection substantially orthogonal to the longitudinal direction of thewire 12B. Further, the wire 12B is provided with a groove 124 whichextends in the circumferential direction and the groove 124 is formed onthe entire circumference of the wire 12B. That is, the wire 12B of thisembodiment has a columnar shape provided with a plurality of the annulargrooves 124. As illustrated in the same drawing, in this embodiment, theplurality of grooves 124 are arranged at the substantially equalintervals in the longitudinal direction of the wire 12B, but theinvention is not particularly limited thereto. The wire 12B of thisembodiment is formed by cutting, pressing, or rolling a wire.

In this way, in this embodiment, since the wire 12B is provided with thegroove 124, the outer surface 121 of the wire 12B partially includes theconcave portion 122 in the longitudinal direction of the wire 12B asillustrated in FIG. 12. That is, in this embodiment, the wire 12B has across-sectional shape in which the outer surface 121 partially includesthe concave portion 122 when the wire 12B is cut along the longitudinaldirection of the wire 12B. FIG. 12 is a cross-sectional view when thewire 12B is cut along the longitudinal direction of the wire 12B.

Further, in this embodiment, since the wire 12B is provided with thegroove 124, the cross-sectional area at one position (for example, aline XIA-XIA of FIG. 10) in the longitudinal direction and thecross-sectional area at the other position (for example, a line XIB-XIBof FIG. 10) in the longitudinal direction are different from each otheras illustrated in FIGS. 11(A) and 11(B). Further, in this embodiment,since the wire 12B is provided with the groove 124, the cross-sectionalshape at one position (for example, a line XIA-XIA of FIG. 10) in thelongitudinal direction and the cross-sectional shape at the otherposition (for example, a line XIB-XIB of FIG. 10) in the longitudinaldirection are different from each other as illustrated in FIGS. 11(A)and 11(B). FIGS. 11(A) and 11(B) are cross-sectional views when the wire12B is cut along a direction substantially orthogonal to thelongitudinal direction of the wire 12B.

In this way, in this embodiment, the concave portion 122 is partiallyprovided in the outer surface 121 of the wire 12B in the longitudinaldirection of the wire 12B similarly to the first embodiment.Accordingly, the liquid medium flowing on the surface of the wire 12Bcollides with the concave portion 122 so that forced convection occursand the flow of the liquid medium becomes turbulent. For this reason,since the heat transfer rate between the wire 12B and the liquid mediumcan be increased, a wide temperature span can be obtained.

The shape of the wire is not particularly limited. For example, asillustrated in FIG. 13(A), a wire 12Ba may have a columnar shapeprovided with a spiral groove 124. The extending direction of the spiralgroove 124 includes the circumferential direction of the wire 12Ba asone element. Alternatively, as illustrated in FIG. 13(B), the wire 12Bbmay have a columnar shape provided with a plurality of grooves 124partially formed in the circumferential direction.

Alternatively, as illustrated in FIG. 13(C), a wire 12Bc may have acolumnar shape provided with a plurality of annular walls 125.Alternatively, as illustrated in FIG. 13(D), a wire 12Bd may have acolumnar shape provided with a spiral wall 125. The extending directionof the spiral wall 125 includes the circumferential direction of thewire 12Bd as one element. Alternatively, as illustrated in FIG. 13(E), awire 12Be may have a columnar shape provided with a plurality of walls125 partially formed in the circumferential direction.

Embodiments heretofore explained are described to facilitateunderstanding of the present invention and are not described to limitthe present invention. It is therefore intended that the elementsdisclosed in the above embodiments include all design changes andequivalents to fall within the technical scope of the present invention.

The configuration of the above-described magnetic heat pump device is anexample, and the heat exchanger according to the invention may beapplied to another magnetic heat pump device of an AMR (Active MagneticRefrigeration) type.

For example, the magnetic heat pump device may include one MCM heatexchanger, a magnetic field changer configured to supply a magneticfield to the MCM and change the magnitude of the magnetic field, firstand second external heat exchangers respectively connected to the MCMheat exchanger through a pipe, and a fluid supplier configured to supplya fluid to the first or second external heat exchanger from the MCM heatexchanger in synchronization with the operation of the magnetic fieldchanger. Further, in the above-described embodiment, the liquid mediumflow direction is changed by using the rotary pump 70 and the switchingvalve 90, but a reciprocating pump may be used instead of the rotarypump 70 and the switching valve 90.

Further, in the above-described embodiment, an example in which themagnetic heat pump device is applied to the air conditioner for home oran automobile has been described, but the invention is not particularlylimited thereto. For example, when an MCM having an appropriate Curietemperature according to the application is selected, the magnetic heatpump device according to the invention may be used for an application inan extremely low temperature range such as a refrigerator or in a hightemperature range to some extent.

Further, in this embodiment, the first and second MCM heat exchangers 10and 20 have the same configurations, but the invention is notparticularly limited thereto. Here, the heat exchangers may havedifferent configurations. For example, the first and second MCM heatexchangers 10 and 20 may use wires having different wire diameters.Further, the twisting pitches of the wires may be different from eachother.

Further, in this embodiment, the MCM heat exchanger includes a singleassembly, but the invention is not particularly limited thereto. Forexample, a plurality of assemblies may be arranged in series along theextending direction of the MCM heat exchanger. In this case, theplurality of assemblies may have the same configurations or differentconfigurations.

EXPLANATIONS OF LETTERS OR NUMERALS

1: magnetic heat pump device

10: first MCM heat exchanger

11: assembly

111: passage

12A, 12Aa to 12Al, 12B, 12Ba to 12Be: wire

122: concave portion

123: convex portion

124: groove

125: wall

13: casing

131: first opening

132: second opening

14: accommodation portion

141: bottom portion

142, 143: side portion

144: opening

15: lid portion

17: first terminal member

171: first connection port

18: second terminal member

181: second connection port

20: second MCM heat exchanger

21: assembly

22A: wire

23: casing

271: first connection port

281: second connection port

30: piston

35: actuator

40: permanent magnet

50: low temperature side heat exchanger

60: high temperature side heat exchanger

70: rotary pump

81 to 82: first and second low temperature side pipes

83 to 84: third and fourth high temperature side pipes

90: switching valve

1. A wire which is formed of a magnetocaloric material having amagnetocaloric effect, wherein an outer surface of the wire partiallyhas at least one of a concave portion and a convex portion in alongitudinal direction of the wire, the concave portion is recessed in aradial direction of the wire, and the convex portion protrudes in theradial direction.
 2. The wire according to claim 1, wherein the wire hasa non-circular cross-sectional shape, and a cross-sectional shape at oneposition in the longitudinal direction and a cross-sectional shape atthe other position in the longitudinal direction have a rotationalsymmetry relationship.
 3. The wire according to claim 1, wherein thewire has a non-circular cross-sectional shape, and the wire is twistedin a circumferential direction of the wire.
 4. The wire according toclaim 2, wherein the cross-sectional shape of the wire includes an ovalshape, a semi-circular shape, or an n-polygonal shape (n is a naturalnumber from 3 to 8).
 5. The wire according to claim 1, wherein across-sectional shape at one position in the longitudinal direction anda cross-sectional shape at the other position in the longitudinaldirection are different from each other.
 6. The wire according to claim1, wherein a cross-sectional area at one position in the longitudinaldirection and a cross-sectional area at the other position in thelongitudinal direction are different from each other.
 7. The wireaccording to claim 5, wherein the wire has a columnar shape having atleast one of the concave portion and the convex portion.
 8. The wireaccording to claim 6, wherein the wire has a columnar shape having atleast one of the concave portion and the convex portion.
 9. The wireaccording to claim 5, wherein at least one of the concave portion andthe convex portion includes at least one of a wall and a groove formedon an outer surface of the wire, and an extending direction of at leastone of the groove and the wall includes at least the circumferentialdirection of the wire as an element.
 10. The wire according to claim 6,wherein at least one of the concave portion and the convex portionincludes at least one of a wall and a groove formed on an outer surfaceof the wire, and an extending direction of at least one of the grooveand the wall includes at least the circumferential direction of the wireas an element.
 11. A heat exchanger comprising: an assembly which isobtained by bundling the wires according to claim 1; and a casing whichaccommodates the assembly.
 12. A magnetic heat pump device comprising:at least one heat exchanger according to claim 11; a magnetic fieldchanger configured to apply a magnetic field to the magnetocaloricmaterial and change the magnitude of the magnetic field; first andsecond external heat exchangers respectively connected to the heatexchanger through a pipe; and a fluid supplier configured to supply afluid from the heat exchanger to the first or second external heatexchanger in synchronization with the operation of the magnetic fieldchanger.